The effects of whole body heat s t r e s s on semen quality have been reported for mice (Okauchi, 1963), rabbits (E1- Shiekh and Casida, 1955;Hiroe and Tamizuka, 1965), r a m s (Djanuar, 1965;Moule and Waites, 1963) and bulls (Casady, Mayers and Legates, 1953). In all cases, one or more of the following was reported at some time post-treatment, usually several weeks: an i n c r e a s e in abnormal s p e rmatozoa, an i n c r e a s e in seminal pH, a d e c r e a s e in spermatozoan motility and concentration, and an i n c r e a s e in seminal fructose. Thibault et al. (1966) found a d e c r e a s e in farrowing rate after gilts were bred with semen f r o m seven boars maintained outside and exposed to temperatures as high as 35°C as compared to seven control boars maintained in an air-conditioned building at 22°C. The diff e r e n c e between the two groups occurred in the period between June and Septemb e r when the outside boars were exposed to the s u m m e r heat. Similar results w e r e noted by Signoret and du Mesnil du Buisson (1968) with a mean t e m p e r a t u r e of 25.5°C outside and 17.8°C inside. Mazzari, du Mesnil du Buisson and Ortavant (1968) applied a local heat treatment to the boar scrotum which raised the t e mp e r a t u r e of the testis to 39.5 ° or 40.5°C for 3 hours. The effect of this treatment was seen 15 to 58 days p o s t -t r e a t m e n t as a s e v e r e d e c r e a s e in spermatozoan concentration and motility. The object of the present study was to a s s e s s the effect of a three day heat s t r e s s on semen quality of boars acclimated to t e m p e r a t u r e s at or below 21.5°C. MATERIALS AND METHODSTwelve sibling p a i r s of six-month old boars were maintained in an a i r -c o nditioned area at 18 ° to 21.5°C with 12 hr of incandescent light p e r day. There w e r e three p a i r s each of purebred Yorkshire (YY), purebred Poland China (PP) and three p a i r s each of the reciprocal c r o s s e s (PY and YP). During a 3-month acclimation period the boars were trained for semen collection using a dummy sow. The eiaculates were collected with a bare hand and strained through one layer of 44 x 36 mesh cheesecloth into a 454 ml vacuum flask p r e w a r m e d to 38°C. Collection was begun as soon as full protrusion had been obtained and continued until the boar voluntarily dismounted from the dummy sow.After the acclimation period one boar of each pair was randomly assigned to be heat stressed. The other boar was used as a paired control. The treated boars were subjected to ambient and radiant t e m p e r a t u r e s of 33°C, 50% RH for 72 hr. During the treatment the control boars were maintained at 20°C, 50% RH. S e m e n was collected from each boar during heat s t r e s s and regularly e v e r y fourth day p o s t -t r e a t m e n t (PT) for 64 days. During heat stYess, rectal t e m p e r a t u r e s were taken at i r r e g u l a r intervals with m e r c u r y -i n -g l a s s t h e r m o m e t e r s . Eight boars

Lactation records (n = 86) from 60 does of four breeds (Californian, New Zealand White, Palomino and White Satin) were analyzed to assess the effects of breed, parity, day of lactation and number of kits on milk production. Breed of doe tended (P less than .07) to be important for mean milk yield according to ANOVA results. Californian does had numerically higher production than did does of the other breeds. Doe body weight, litter size born alive and weaned and litter weaning weight, likewise, were not influenced (P greater than .05) by breed of doe. Significant linear and quadratic relationships were found between milk production vs day of lactation, and milk production vs number of kits. However, breed x days and breed x number of kits interactions (P less than .05) indicated that the individual breeds responded differently to two of these effects. Peak lactation occurred at approximately 20 d after kindling. As kit number increased, milk yield also increased to a predicted maximum when 12 kits were suckling. Parity tended (P less than .10) to influence lactation yield in a curvilinear manner, increasing steadily through the seventh parity and declining thereafter. A nonsignificant residual correlation (.34) between milk production and doe body weight was observed. Corresponding correlations between milk production were high for litter size born alive and weaned (r = .62 and .87, respectively) and litter weaning weight (r = .86). Although lactation curves are unique to each particular breed, milk yield is influenced by several factors.

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